A235636 -id:A235636 - cp's OEIS frontend

A235637 Primes whose base-7 representation also is the base-6 representation of a prime.

2, 3, 5, 19, 61, 89, 127, 131, 173, 211, 229, 257, 281, 383, 397, 421, 463, 467, 523, 547, 593, 617, 719, 757, 761, 859, 883, 911, 953, 967, 971, 1069, 1097, 1153, 1163, 1181, 1303, 1307, 1429, 1433, 1471, 1489, 1531, 1583, 1597, 1723, 1741, 1867, 1877, 1951, 1979, 1993, 2437

Offset: 1

M. F. Hasler, Jan 13 2014

This sequence is part of the two-dimensional array of sequences based on this same idea for any two different bases b, c > 1. Sequence A235265 and A235266 are the most elementary ones in this list. Sequences A089971, A089981 and A090707 through A090721, and sequences A065720 - A065727, follow the same idea with one base equal to 10.

			E.g., 19 = 25_7 and 25_6 = 17 are both prime.

Robert Price, Table of n, a(n) for n = 1..14278
M. F. Hasler, Primes whose base c expansion is also the base b expansion of a prime

Cf. A235636, A235265, A235266, A152079, A235461 - A235482, A065720 - A065727, A235394, A235395, A089971 ⊂ A020449, A089981, A090707 - A091924, A235615 - A235639. See the LINK for further cross-references.

is(p,b=6,c=7)=vecmax(d=digits(p,c))

forprime(p=1,3e3,is(p,7,6)&&print1(vector(#d=digits(p,6),i,7^(#d-i))*d~,",")) \\ To produce the terms, this is more efficient than to select them using straightforwardly is(.)=is(.,6,7)

cp's OEIS Frontend

A235637 Primes whose base-7 representation also is the base-6 representation of a prime.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

PARI

PARI